[pysrc2cpg] Fix tab handling in parser grammar. (#5703)

Old implementation was not able to handle more than 2 tabs.

Author: ml86

joern-cli/frontends/pysrc2cpg/pythonGrammar.jj

@@ -822,7 +822,13 @@ SPECIAL_TOKEN: {
 
 <INDENT_CHECK> SKIP: {
   <INDENT_CHECK_SPACE: " "> { currentIndent += 1; }
-| <INDENT_CHECK_TAB: "\t">  { currentIndent = currentIndent / 8 + 8; }
+| <INDENT_CHECK_TAB: "\t">  {
+  // The "/ 8 * 8" rounds down to the closest multiple of 8.
+  // This is needed to handle python 2 mixed space and tab use cases
+  // where tab is not strictly counted as 8 spaces but rather adds the
+  // amount of spaces to get to the next multiple of 8.
+  currentIndent = currentIndent / 8 * 8 + 8;
+}
 | <INDENT_CHECK_NEWLINE: "\n" | "\r"> { currentIndent = 0; }
 | <INDENT_CHECK_END_OF_MEDIUM: "\u0019">
 | <INDENT_CHECK_END: ~[]> {

joern-cli/frontends/pysrc2cpg/src/test/scala/io/joern/pythonparser/ParserTests.scala

@@ -350,6 +350,7 @@ class ParserTests extends AnyFreeSpec with Matchers {
         |  z = (x,y)
         |a""".stripMargin
     )
+    testT("def init():\n\tmatch x:\n\t\tcase 'C':\n\t\t\tz = 1")
   }
 
   "explicit line joining tests" in {